Virtual Organizations as Normative Multiagent Systems

1. Virtual Organizations as Normative Multiagent Systems Guido Boella Università di Torino, guido@di.unito.it Joris Hulstijn Vrije Universiteit, Amsterdam, jhulstijn@feweb.vu.nl Leendert van der Torre CWI, Amsterdam, torre@cwi.nl

2. Virtual Organizations • Virtual Organizations: individuals and institutions that need to coordinate resources and services across institutional boundaries (Foster et al) • Infrastructures: e.g. GRID, CSCW, KM, … • Users form a virtual community, with shared norms and objectives. • Align community norms with infrastructure rules? • Client-server: global policies, but no local control • Peer-to-peer: local control, but no global policies • Need a conceptual model ofnorms at different levels of control. Boella, Hulstijn, van der Torre

3. Normative Multiagent Systems • Normative system: set of norms (obligations) with an enforcement mechanism. • Multiagent system: set of autonomous agents with beliefs, goals, actions ... • Model interaction between agents by recursive modeling • Model normative system N as any other agent [Boella & Van der Torre KR’04,AAMAS’04] Boella, Hulstijn, van der Torre

4. Overview (i). Example (ii). NMAS (iii). Conclusions • How can the behavior of an individual agent in a virtual organization be described? • How can agents change a virtual organization? • How can agents in a virtual organization establish normative relations or contracts with each other? • How can we deal with norms that operate at different levels of control? Boella, Hulstijn, van der Torre

5. (i). Example

6. entitle access request access ? a3 a2 a1 user storage provider owner Distributed Access Control • Global norms, but local access control. • owners have the right to entitle access to a resource • storage providers can grant or withhold access [Firozabadi and Sergot 2002] • So a2 must • check ID a1, • check entitlement a1 • weigh obligations against own goals Boella, Hulstijn, van der Torre

7. Observations • Dynamic: agents can enter, leave and alter the normative system. • Interactive: agents can agree on a contract (set of mutual obligations), enforced by N. • Obligations are effective only when accompanied by an enforcement mechanism. • Violation detection and sanctioning can be delegated to other agents. • Roles: subjects, defenders, normative system Boella, Hulstijn, van der Torre

8. (ii). NMAS

9. Observations < Beliefs Goals Goal Generation Goals Planning & Scheduling Actions Individual Agent • Focus on goal generation • Use sets of production rules P Q to represent beliefs and goals, with a priority order <. • Belief rules: information about current state • Goal rules: information about ideal future state Boella, Hulstijn, van der Torre

10. Example 1. Belief: at party 2. Goal: at party drink beer 3. Goal: drink beer smoke cigarette 4. Goal: ¬smoke cigarette Priority: 1 > { 2 , 4 } > 3 Outcome: { at party, drink beer, ¬smoke cigarette } , Boella, Hulstijn, van der Torre

11. Recursive Modeling agent Adeliberates about optimal decision – considers optimal decision of agent B agent B deliberates about optimal decision – considers optimal decision of agent A agent Adeliberates about optimal decision – considers optimal decision of agent B • Profile (set of P Q rules) depends on role. • Used for trust and deception. Boella, Hulstijn, van der Torre

12. Joris Hulstijn Thursday January 6, lunch ticket Constitutive Rules • Establish institutional facts by constitutive rules [Searle 1995]. • E.g. counts as an entitlement to lunch, at the HICSS conference. • “P counts as Q in institutional context C” whenever CPQis a belief ofN Boella, Hulstijn, van der Torre

13. Norms Obligation of A to N to bring about P in context C, under sanction S iff 1. Goal of N: CP 2. Goal of N: (C¬P)  Viol(A, ¬P) 3. Goal of N: ¬ Viol(A, ¬ P) 4. Goal of N: Viol(A,¬ P) S 5. Goal of N: ¬S 6. Goal of A: ¬S 7. Goal of A: ¬P A: 6 > 7, N: 2 > 3, 4 > 5 My wish is your command? Boella, Hulstijn, van der Torre

14. Dynamics • The fact that normative rules 1-6 hold, is itself an institutional fact, i.e. a belief of N. • A performative speech act counts as the creation of an institutional fact in context C, provided … • preparatory conditions hold, and • sincerity, propositional and essential conditionshold. • Owner a entitles b access to d, meanseither 1. create an obligation for all to grant b access to d, or 2. create a credential, used with a general access obligation. Boella, Hulstijn, van der Torre

15. (iii). Conclusions

16. A : N A N N : A A N A : A A N N : N A N Four kinds of Structures • A regards N - e.g. decide to violate or not • N regards A’s behavior - e.g. decide how to enforce • A1 regards A2 given N - e.g. decide whether to trust • N1 regards N2, given A’s behavior given N - e.g. decide to delegate or not Boella, Hulstijn, van der Torre

17. Conclusions Virtual organizations as normative multiagent systems. • Individual agents are modeled goal generation, based on beliefs, goals and priorities. • Dynamics can be captured by constitutive rules. • Using recursive modeling and interaction, complex normative relations can be broken down into four types: A:N, N:A, A:A (N) and N:N (A). • Norms at different levels of control, can be dealt with by delegation to embedded normative multiagent systems, leading to different roles: subjects, defenders and the normative system. Boella, Hulstijn, van der Torre

18. References G. Boella and L. van der Torre. Regulative and constitutive norms in normative multiagent systems. KR’04. G. Boella and L. van der Torre. Attributing mental attitudes to normative systems. AAMAS’04. J. R. Searle. The Construction of Social Reality. The Free Press, New York, 1995. Ronald M. Lee. Bureaucracies as deontic systems. ACM Transactions on Information Systems, 6(2):87 – 108, 1988. Jones, A.J.I. & Sergot, M.J. On the characterisation of law and computer systems In:Deontic Logic in Computer Science, Wiley 1993, 275 -- 307. L. Kagal, T. Finin, A. Joshi Trust-Based Security in Pervasive Computing Environments, Communication of the IEEE, 34 (12), 154 – 157, 2001 Boella, Hulstijn, van der Torre

19. entitle access request access ? a3 a2 a1 user storage provider owner Distributed Access Control (2) • Goal of N: req(a3,d) cred(a1,a3,d)  acc(a2,a3,d) • Goal of N: req(a3,d) cred(a1,a3,d)  ¬ acc(a2,a3,d)  Viol(a2,¬ acc(a2,a3,d)) • Goal of N: ¬ Viol(a2, ¬ acc(a2,a3,d)) • Goal of N: Viol(a2, ¬ acc(a2,a3,d))  ban(a2) • Goal of N: ¬ ban(a2) • Goal of a2: ¬ ban(a2) • Goal of a2: ¬ acc(a2,a3,d) for a2: 6 > 7 for N: 2 > 3, 4 > 5 Boella, Hulstijn, van der Torre

20. Example Obligation of a to n not to overfish in spring, under sanction of paying a fine. • Goal of n: spring ¬ overfish • Goal of n: spring  overfish  Viol(overfish, a) • Goal of n: ¬Viol(overfish, a) • Goal of n: spring  Viol(overfish, a)  fine • Goal of n: ¬ fine • Goal of a: ¬ fine • Belief of a,n: spring • Goal of a: overfish Works only in case Desire 8 < Desire 6 Boella, Hulstijn, van der Torre